1. Field of the Invention
The present invention relates generally to a electric power supples and, more specifically, to a power supply with a small and very limited capacity power source and with a small and very limited power storage capacity for powering electrical devices that require intermittent, momentary, high current pulses.
2. Description of the Prior Art
The recent availability of more reliable small, self-contained, renewable power sources, such as rechargeable batteries, solar cells, and the like have contributed to the advent of small, portable electronic products, equipment, controller, and other devices that can be located and operated independent from conventional public utility electric power grids, or other large capacity power sources. The issue of initial start-up of power supplies for small or portable electronic devices from dead or discharged rechargeable battery conditions is not so much of an issue, when chargers or re-chargers for such electronic devices can simply be plugged into public utility electric power grids or other large power sources. However, when faced with situations in which plugging into such a large power source for re-charging is inconvenient, unavailable, or simply not wanted, especially in combination with a desire or an economic necessity of making such portable electronic products, equipment, controllers, or other devices as small and efficient as possible, available options for such small, efficient, and dependable power supplies become quite limited.
The power supply described in co-pending U.S. patent application, Ser. No. 09/131,254 (now issued U.S. Pat. No. 6,194,793), which is incorporated herein by reference, is especially useful for powering a load, such as a microprocessor or other electric circuit, that requires a constant voltage, such as 5.0 volts, with a low capacity, sometimes lower voltage, and sometimes intermittent power source, such as a solar cell, small capacity battery, thermal electric generator, or the like. That power supply combines a low capacity or intermittent power source, power storage device, a power converter for converting either lower or higher voltage power to a steady output voltage, and a control feature, which prevents the power converter from operating until the voltage in the power storage device is high enough for the power converter to operate at a minimum efficiency level to facilitate from a dead or low storage charge state using only the low capacity or intermittent source power. It also includes an embodiment in which a secondary load, such as a solenoid, can be powered from the energy storage device, but only when the voltage in the energy storage device is built up high enough to not only operate the power converter efficiently for powering the microprocessor controller circuit, but also high enough to operate the solenoid.
A primary advantage of the power supply circuit of that Ser. No. 09/131,254 (now U.S. Pat. No. 6,194,793) is that it eliminated the need for plugging into public utility electric grid or large electric generator to start and operate a load and made it feasible to use and rely on only a low-voltage, rechargeable battery and a low-capacity, even intermittent, power source, such as a solar cell, for a self-starting, efficient, and reliable power supply. Consequently, it provided a smaller, less expensive, and more reliable power source than was available before.
However, when that power supply of U.S. patent application, Ser. No. 09/131,254 (now U.S. Pat. No. 6,194,793) is also used to power an intermittent or periodic, high-current load or pulse, such as when it is operating a solenoid, transmitting a burst of data by radio frequency (RF) or micro waves, making a motor controlled adjustment, operating an alarm, or the like, the marginal capacity of that power supply is limited, and it can become unreliable. For example, if the storage device is a rechargeable battery, which is not sufficiently recharged when called upon to power such a high-current load, or which is exposed to cold weather in which its power capacity is substantially diminished, it may not be able to provide sufficient power, even for short bursts, for reliable operation. Of course, a larger battery with more capacity and a higher working voltage could improve reliability, but it would sacrifice physical size, weight, and cost advantages of the smaller battery.
Accordingly, it is the general object of the present invention to provide a more reliable apparatus and method for powering high current switching or high current, short pulse operation of electrical devices with small energy source and energy storage components.
Another general object of the present invention is to provide an apparatus and a method for improving the efficiency of electrical energy delivery to an intermittent, short, but high current, load from a small, limited capacity, battery storage device.
Still another general object of the present invention is to provide an apparatus and a method for enabling initial xe2x80x9cdeadxe2x80x9d battery charging and power start-up of low-powered instrumentation or equipment to operate controlled, intermittent, short, but high current, loads along with more constant powered control components.
A more specific object of this invention is to improve high current switching capabilities and reliability of the power supply described in co-pending U.S. patent application, Ser. No. 09/131,254 (now issued U.S. Pat. No. 6,194,793), which is incorporated herein by reference.
Another specific object of this invention is to improve reliability and performance of the power supply described in U.S. patent application, Ser. No. 09/1331,254 (now U.S. Pat. No. 6,194,793) in initial dead battery start-up or in other dead or very low battery situations in applications where the power supply is used to power a high current switching or other intermittent, high current functions.
Still another specific object of this invention is to provide improvements in the power supply circuit of U.S. patent application, Ser. No. 09/131,254 (now U.S. Pat. No. 6,194,793) that extend the ability to power reliable, high current switching and other intermittent, high current pulse loads to use even smaller capacity and lower voltage power storage devices and power sources.
Additional objects, advantages, and novel features of the invention shall be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by the practice of the invention. The objects and the advantages may be realized and attained by means of the instrumentalities and in combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects and in accordance with the purposes of the present invention, as embodied and described herein for enabling example, but not for limitation, a power supply in accordance with the present invention may include a combination of an energy storage capacitor and associated switch and control components for discharging energy in intermittent, short, pulses from the energy storage capacitor to power a controlled device with a rechargeable energy storage device, and energy converter that provides energy from the energy storage device to the energy storage capacitor and to the associated switch and control components at a constant voltage, but only when the voltage of the rechargeable energy storage device is high enough for the energy converter to operate at a minimum threshold efficiency level. An energy recharge source provides electric energy to charge and maintain electric energy in the rechargeable energy storage device. The constant voltage energy from the energy converter can be provided directly to the energy storage capacitor, or it can be routed through a current limiting resistor or through a logic controller, depending on the application and on reliability issues associated with the application.
To further achieve the foregoing and other objects, the present invention further comprises a method of converting energy from a rechargeable energy storage device to a constant voltage output to an energy storage capacitor and associated switching and control components, but only when voltage of the rechargeable energy storage device is high enough for the energy converter to operate at a minimum threshold efficiency level, and discharging energy from the energy storage capacitor in short, intermittent pulses, to power a controlled device. The invention can also include recharging the rechargeable energy storage device with electric energy from a small capacity energy recharge source, such as a solar cell or panel, battery, thermal electric generator, wind powered generator, or the like. The constant voltage electric energy from the energy converter can be fed directly to the energy storage capacitor and to the associated switching and control components in parallel, or it can be fed through, and controlled by, control components to the energy storage capacitor.